11.3. Client-Side JavaScript

Client-side JavaScript is the name
given to JavaScript code that is embedded within an HTML file and
executed by a web browser. In addition to the core objects described
in the previous section, client-side JavaScript code has access to a
number of other objects that represent the web browser, the document
displayed in the browser, and the contents of that document.
Client-side JavaScript programs are usually event-based, which means
that JavaScript event handlers are executed in
response to user interactions with the browser and the document. The
client-side JavaScript scripting framework is powerful enough to open
substantial security holes in web browsers. For this reason, web
browsers typically restrict the actions of client-side scripts. This
section starts by explaining how JavaScript code is embedded in HTML
files, then goes on to introduce the client-side JavaScript objects,
JavaScript events and event handling, and JavaScript security
restrictions.

11.3.1. JavaScript in HTML

JavaScript code may be embedded in HTML
files in the form of scripts, event handlers and URLs, as detailed
below.